DE3006742A1 - DEVELOPMENT DEVICE FOR AN ELECTROPHOTOGRAPHIC COPIER - Google Patents

Description

The invention relates to a magnetic brush developing device for use in an electrophotographic Copier, particularly a magnetic brush developing device for use in a one-component developer known per se.

In an electrophotographic copier using a magnetic brush developing device Obtain a copied object so that reflected light from an original to be copied to a uniform projected charged photosensitive element, an electrostatic latent corresponding to the original Image formed, the latent image to make it visible, developed with a developer and then like that it is fixed or is only fixed after it has been transferred to a transfer paper such as plain paper has been. The developer, not shown, is housed in a development chamber in which a cylindrical sleeve, which is made of non-magnetic material, is arranged so that they are in the vicinity of the Surface of the photosensitive member is and that a part of the sleeve is immersed in the developer; inside this socket is a plurality of magnets near the inner surface of the socket and in a predetermined one Spaced apart, and the socket and the magnets are formed so that they are relative to each other can turn. Accordingly, the developer in the developing chamber when the sleeve or the rotation Magnet transported along the socket surface and a visible egg on the photosensitive element thereby formed so that the developer comes into contact with the surface of the photosensitive member. At the time where such a developer is transported out of the developing chamber, that is to a certain fixed height set on the socket, with a

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Adjustment plate that is close to the outer surface of the Socket is arranged. In other words, the developer adhering to the socket surface becomes in the form of brush-like tufts transported to the development position. Such a developing device as described above Art is known as a magnetic brush developer.

Most of the electrophotographic copiers now popular use a developer, magnetic powder as so-called. Carrier and fine-grained colored resin as so-called. Toner, which are constructed independently of each other, and a such a developer is referred to as a two-component developer. In contrast to the two-component developer a developer consisting only of toner has been developed as a so-called one-component developer. Due to the The fact that such a type of developer comprises magnetized toner containing magnetic substances in the Resin and possibly contains dye, density fluctuations of the copied image, toner consumption, such as it occurs when using two-component developer, is not present, and thus there are no density sensing devices whatsoever, special toner refills and carrier changes are required, and many result Advantages of making the developing device itself compact, etc. Due to the above-mentioned circumstances, become One-component developer gradually used in practical operation.

In addition, the two-component developer usually has a carrier which is a coarse-grained magnetic one Substance with a diameter of about 50 to 200μ and a fine-grain toner with a diameter of contains about 5 to 20 μ, and iron powder is used as a magnetic substance for the carrier. That

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The mixing ratio of the carrier and the toner is about 2 to 10% by weight of the toner based on 100 parts by weight Iron powder.

In the two-component developer, the iron powder carrier adheres to the socket under the influence the magnetic force generated by the plurality of magnets fixedly mounted in a space of the socket, and the carrier is transported as the sleeve rotates, while the toner is carried along with the carrier since the toner is strongly electrostatically adhered to the surface of the iron powder carrier, so it is rare that the toner is scattered during a transport route. Due to the fact that the weight of the carrier particles high and its diameter is large, it is also rare for it to flow out through a narrow opening, etc.

On the other hand, in the case of a one-component developer, there is no such large-diameter grain what corresponds to the carrier in the two-component developer is present; in addition, are resin components contained in large amounts as particles in the developer, and the component of the magnetic substance is at most 20 to 80% by weight based on 100 parts by weight of developer, which is far less than with the two-component developer .

In the case where a one-component developer of the above type for a magnetic brush developing device is used, is consequently due to the socket or group of magnets that are connected to a reasonable rotational speed of, for example, 300 revolutions per minute in a developing device turns, developer thrown up and spread as a haze or haze and causes impurities in and

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outside the development chamber or penetrates bearings for the rotating shaft of the bushing or a group of magnets and increases the friction during rotation and thus inhibits the rotation of the shaft. The adhesive force of the one-component developer at the socket is relatively weak because of the proportion of the magnetic component contained in the developer is lower. Because of the foregoing reasons, there may be an adhesive force on the magnetized portion of the developing device cannot be achieved to the same extent as with the two-component developer, despite the compensation that is made by the increasing magnetic force of the group of magnets. Thus, the thickness of the developer layer, which is formed on the socket is thin and has a value of about 1 to 1.5 mm, and consequently becomes the distance between an adjustment plate for the formation of brush-like tufts of developer and the socket pretty narrow. The developer, which is transported through the narrow distance, with which its height is adjusted spreads outward and gathers at both ends of the setting plate because of the weak adhesive force on the socket. This affects the result in the subsequent development.

Unlike a toner refill from a two-component developer the replenishment amount of the one-component developer has no direct influence on the image density. This is an advantage of the one-component developer that a user can specify a refill amount of his choice, but if the refill is made so that the If the bearing of the rotating shaft bushing or a group of magnets is immersed, it is to be feared that particles may become entrained penetrate a bearing part and increase the load or friction of the rotation and thus an obstruction or danger represent for the camp.

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So far, there are some electrophotographic copying machines has become known with a magnetic brush developing device and using a one-component developer, for example from JP-OS 52-101Λ6 and the JP-OS 52-347 ^ 2, most of which are of the type that the developer only comes out in a required amount a toner supply part located above the socket in the developing chamber of the developing device is built in. However, there is no means of solving the specific problems discussed above solve that occur with the one-component developer.

The object of the invention is therefore to create an arrangement that avoids the disadvantages mentioned the use of a one-component developer or a so-called magnetic toner ensures correct operation guaranteed with a magnetic brush developing device.

According to the invention there is essentially provided a distribution plate or a partition plate in the vicinity of the To arrange the surface of the sleeve at the two ends in the axial direction of the sleeve of the developing device, the partition plate is preferably formed to have a thickness of 0.15 to 1.0 mm and a spacing between itself and the socket surface that is smaller than 0.35 mm. In the case where the partition plate is not in Contact with the socket surface is set, an additional separating part is arranged, which is connected to the separating plate is in contact, and the distance between the additional partition and the socket surface becomes preferable held to a value of less than 0.35 mm.

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The invention will be explained below with reference to the description of exemplary embodiments and explained in more detail with reference to the accompanying drawings. The drawing shows in

Fig. 1 is a schematic diagram for explaining the construction of an embodiment of an electrophotographic Copier using a magnetic brush developing device;

Fig. 2 is an enlarged partial cross section of a magnetic brush developing device an embodiment according to the invention;

Fig. 3 is a perspective view to explain the essential parts of the invention Embodiment;

Fig. 4 is a perspective view of the partition plate and related parts;

FIG. 5 is a graph for explaining FIG Changes in the amount of developer leaked depending on changes in the distance between the partition plate and the socket surface; "

Fig. 6 is a perspective illustration for explanation the structure of the adjustment plate according to the invention; and in

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. ₁₀ - 30Q6742

FIG. 7 is a schematic illustration to explain the arrangement of the partition plate with respect to FIG Rifle.

In the illustration according to FIG. 1, an original 2 is illuminated which is placed on a movable copying plate is laid, with a light beam from the lamp 3 when the copy platen 1 moves, and a reflected one Light beam from the original to be copied is reflected through the reflecting mirror U and the lens 5 onto the projected photosensitive element 7 in the form of a sheet or sheet, which on the peripheral surface of a rotating drum 6 is attached. Since the photosensitive member 7 is previously provided with a charging electrode 8 uniformly has been charged, at the time when the reflected light from the original 2 is projected thereon, generates an electrostatic latent image corresponding to the original. The electrostatic latent image becomes developed by the developing device 9 and converted into a visible image or toner image, and then by of the transfer electrode 13 is transferred to an unillustrated transfer paper drawn from the hopper 10 by a feed roller 11 and a pair of Support rollers 12 is supplied. Then, the transfer paper made with the photosensitive member 7 is in contact stands, separated therefrom with an electrostatic force with the aid of a separator without reference numerals and transported by the transport device IU to a fixing device 15, fixed there and then in a receptacle 16 disposed outside the body of the machine.

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The photosensitive member 7 in the form of a sheet or The arc is on the peripheral surface of the rotating drum 6 and attached around it with a plate 17 resting on part of the drum 6, the two ends of the photosensitive Element 7 assigned, is provided and is replaced by hand by an operator after carried out a predetermined number of copying operations has been by opening the top cover plate 18 of the copier, which is located near the top of the rotating Drum 6 is provided.

The developing device 9 shown in Figs. 2 and 3 is a magnetic brush developing device which is disposed adjacent to the rotating drum 6; inside the housing 91, a sleeve 92 made of non-magnetic and electrically conductive material with a rotatable shaft 92a is suspended and arranged to be rotatable in a position close to the photosensitive member 7 of the rotating drum 6, for the sake of simplicity in FIG In the following description, the photosensitive element 7 in "its combination with the drum 6 is also referred to as a photorensitive drum. Inside the rotating sleeve 92 are a main magnet 2 0 and five pieces of additional magnets or auxiliary magnets 21, 22, 23, 2k and 25 placed on a carrier 26 for development so that they are near and opposite the inner surface of the sleeve 92 with both magnets 20-25 and carrier 26. The polarity of these magnets is alternating N and S. A Space for accommodating the developer, namely the development chamber 93, is inside the housing 91 and on the opposite side of the photosensitive drum opposite to the sleeve 92 arranged. A setting

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plate 27 for adjusting the thickness of the one-component developer, adhering to the socket is attached to a part of the housing 91 with screws below the outside the rotating sleeve 92 attached.

As can be seen from FIG. 3, the adjusting plate 27 is a plate whose length is almost is the same as that of the rotating sleeve 92 and is formed so that the two ends are slightly wider. This wider part 27a is mainly at the top of the non-magnetic area and near the socket 92 arranged, or arranged in contact with the socket 92, using in more detail below described auxiliary materials. Thus is the adjustment plate 27 able to provide protection against leaking developer in the adjustment range as well as accumulation to prevent in the end area.

It should be noted that the development chamber 93 is formed from part of the sleeve surface, a part of the housing 91, the setting plate 27 and a bent part of the housing, which is provided without a reference number, which located in the upper area of the socket is formed. A component with the bent part described above can be formed separately from the housing 91. The refill cartridge 94 is attached to the top of the developing device 9 loaded for developers from outside. A certain standard amount of one-component developer is in a sheet-shaped form Containers of the refill cassette 94 stored, i.e. held in the housing 91 with guide rails in the housing. For this reason, two projections 94a are formed at the end of the refill cassette 94 and project radially outward. Accordingly, the refill cassette can be smoothed along the rails using the projections insert.

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After loading, the cassette can be rotated when the projections are outside the side wall 91a of the housing 91 are located. If necessary, replenishment can be done by placing the developer in the development chamber 93 drops by turning the refill cassette 94 by hand through 180 ° from the outside of the device turns.

Due to the fact that the diameter of the developer particles is small, that in the developing chamber 9 becomes 3 stored developer is whirled up like mist in the developing chamber 93 by the rotation of the rotating sleeve 92, and at the same time, the developer migrates around both ends of the rotating sleeve 92, and the particles penetrate the pivot bearing, not shown in the drawing, and increase the rotational load of the rotating Bushing 92, which in turn results in seizure. To provide protection against the above-mentioned impairments To offer, the partition plate 30 is near both ends of the rotating sleeve 92 inside the developing chamber 93 arranged. The partition plate 30 is fastened from the inside with a fitting part or fastening part 31, which is fixed to the side wall 91a of the housing 91 with screws from the outside; it is more expedient to when the additional partition part 32 is interposed between the partition plate 30 and the fixing part 31 is (see. Fig. Ό. The partition plate fastening part 31 consists made of non-magnetic metal or a non-magnetic substance such as synthetic resin and its circular ones Surfaces 31a lie at a certain distance from the surface of the rotating sleeve 92 in the operating state opposite to.

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3QQ6742

- in -

The partition plate 30 is formed as a thin plate made of a non-magnetic material such as phosphor bronze is used; preferably, its thickness is about 0.15 to 1.0 mm for a developer having a particle diameter from 5 to 20 u, it being particularly suitable if the thickness is in the range between 0.2 to 0.3 mm lies. It is important that the distance between the circular edge 30a and the surface of the rotating Bushing 92 prevents developer from leaking from both ends of the rotating bushing in the axial direction, as a result of the experiment, it was found that a value less than 0.35 mm apart is preferable.

Fig. 5 shows the results of measurement of the relative amounts of the leaked developer depending on the change in the distance between the partition plate 30 and the surface of the rotating sleeve 92 in the event that the distance between the partition plate 30 and the end edge of the magnetized area is within values of 1 to 6 mm. From this illustration, it can be seen that when the distance has a value of 0.35 mm or more is reached, the amount of material leaking increases dramatically. However, there is a realistic problem for mass production, the difficulty of determining the distance between the partition plate 30 and the surface of the to make rotating bushing 92 smaller than 0.35mm. Here, in the case where the partition plate 30, for example was made of phosphor bronze, the problem of accuracy for the distance between the partition plate 30 and the rotating bushing 92 solved in that an additional separating part 32 between the separating plate 30 and the fastening part 31 interposed and also its circular edge 32a with the surface of the rotating sleeve 92 was brought into contact, as difficulties such as damage to the surface of the socket occur when

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the partition plate is in contact with the socket. The additional separating part 32 consists of a non-magnetic material and is designed as a deflectable plate which has stable repairability, and plastic films are preferably used that do not cause damage to the surface of the socket even if they are in contact with one another, for example films made of Polyester, polycarbonate, and the like, which are commercially available under the names polyimide, teflon, mylar, and so on. The preferred thicknesses of the additional separating part 32 are between 0.15 mm and 1.0 mm, in particular between 0.2 mm and 0.3 mm. The additional partition 32 must be resistant to heat generated by friction with the rotating sleeve 92 and also be wear-resistant, since the circular edge 32a of the additional partition 32 is always in contact with the surface of the rotating sleeve 92.

In addition, in order to protect against the occurrence of the effect that the developer is dispersed and outside of the both ends of the adjusting plate 27 is accumulated when the developer is of the height of the adjusting plate 27 is set and transported out of the developing chamber 93, the distance between the upper end of the wider parts 27a provided at both ends of the adjustment plate 27 and the surface of the rotating sleeve 92 is also preferably set to 0.35 mm or less.

Similar to the partition plate 30, however, the adjusting plate 27 is made of a comparatively hard material such as metal or hard plastic, etc., so that there arises a problem that the surface of the bushing is damaged and the torque is made too large, etc. In addition

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mass production problems arise the precise adjustment of the distance between the upper edge of the wider parts 27a of the adjusting plate 27 and the surface of the rotating sleeve 92 of 0.35 mm or less on; these problems in connection with the accuracy of the distance have been solved by adding an additional Adjusting plate 28 has been brought into contact with the wider part 27a, as shown in FIG. Preferably the additional adjusting plate 28 is made of a material of the same type as that of the additional separating part 32 and the thickness of the additional adjusting plate 28 is set to a value of 0.15 to 1.0 mm. These additional adjustment plate 28 is with the surface of the rotating sleeve 92 on the upper edge of the adjustment plate in touch.

In addition, it has been found that the position where the partition plate 30 is disposed opposite the rotating sleeve 92 has a great influence on the amount of developer leakage. As shown in detail in FIG. 2, the group of magnets 20 to 25 is arranged inside the rotating sleeve 92 and the magnetized area M is formed, as indicated in FIG. 7. As a result, it was found that the distance 1 between the end of the magnetized area M and the partition plate 30 located at the top of the non-magnetized area N has a great influence on the amount of developer, and the following results were obtained in experiments .

The amount of emerging or leaking developer per unit of time has the following values:

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Distance 1 (mm) Leakage condition of the developer

(g / h)

0 Compressed, solidified and closed

clumped together in a lump

1-6 0-0.3H

6 <T 3.2 to U, 3

From the above results it can be seen that the distance 3. is preferably in the range from 1 to 6 mm. In the event that 1 <1 mm, i.e. in the case where the separating plate 30 is particularly close to the end of the magnetized Area M is arranged, a gap between the circular edge 30a of the partition plate 30 and the surface the rotating sleeve 92 is clogged with developer and the developer is compressed and formed into a lump clumped together as the rotating sleeve 92 continues to rotate.

The developer in the form of a lump is destroyed by any impact or the like, becomes one small lump and allows the developer to enter the developing chamber 93. If this small lump to the point is brought between the adjusting plate 27 and the rotating bushing, it affects the height adjustment function of the adjusting plate 27 and the part of the small lump alone has insufficient height of the developer layer or brush-like tufts, creating the effect of white spots. It goes without saying that this is one represents fatal error in copied objects.

On the other hand , if 1 > 6 mm, that is, if the partition plate 30 is at a considerable distance from the edge of the

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3.QQ6742

magnet is ated area! ^ is arranged, takes the Amount of developer due to the distance between the Separation plate 30 and the surface of the rotating sleeve emerges quickly and the leaked or leaked Quantity has a very considerable value, and as a result, the rate of utilization of the developer is markedly decreased. Of the The reason for this is that the amount of leaked or leaked developer from three to 4 grams per hour is an amount equal to the amount of toner contained in 100 grams of a two-component developer is.

In the above, the novel Arrangement in connection with a magnetic brush developing device with rotating sleeve explained, the invention of course in the same way with magnetic brush developing devices with rotating Magnets can be used, the same also applies to development devices in which the development chamber is arranged under the rotating sleeve, as is the case with copiers, the two-component developer use; the same applies to development facilities in which the development chamber is arranged on the side of the rotating sleeve. If also in the described embodiment an additional partition and an additional adjustment plate can be used, so it is not necessary to use such additional separators and an additional adjustment plate if the distance between the surface of the rotating bushing and the partition plate and a wider part of the adjustment plate coincide with a keep the good utilization factor in the production within the range of 0.35 mm.

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With the novel arrangement, it is possible to prevent developer particles from getting into the lag? Of the socket or enter the group of magnets, increasing the rotating load and causing the rotating shaft to seize, by placing the partition plates near both ends of the sleeve in the longitudinal direction at a magnetic brush developing device arranges using a one-component developer; it is also possible to exit or reduce developer leakage considerably by reducing the distance between the separation plate and the surface of the socket and the distance between the adjustment plate and the surface of the socket below of 0.35 mm. In addition, it is possible to considerably increase the leakage or leakage of developer Reduce that you keep the partition plates at a distance in the range of 1 to 6 mm from the edge of the magnetized Area. Eventually, developer can build up on either end of the developer layer can be prevented by setting. In this way, problems that arise due to the special Property of the developer used when a one-component toner in magnetic brush developing devices used, solve with a simple construction.

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Claims (9)

Henkel, Kern, Feuer & Hänzel patent attorneys Registered Representatives before the European Patent Office Konishiroku Photo Industry Co., Ltd. MöhlstraBe 37 Tokyo, Japan D-8000Munich80 Tel .: 089 / 982085-87 Telex: 0529802 hnkl d Telegrams: ellipsoid Feb 22, 1980 Developing device for an electrophotographic copier Claims Developing device for a copier for use with a one-component developer, with a Housing, a socket made of non-magnetic material and a large number of magnets inside the Bushing, which is a layer or thirst-like tuft of developer on the bushing by the relative Form rotation between each other, characterized by an adjustment plate (27) which is located in the vicinity of the Surface of the bushing (92) is arranged and the height of the adhering to the surface of the bushing (92) Developer adjusts, and by separating plates (30), which are near the two ends of the socket (92) are arranged and leakage of the developer in the axial direction at both ends of the book 6e (92) and prevent the developer from accumulating after adjusting the height with the adjusting plate (27). 030036/0772 2. Device according to claim 1, characterized in that the thickness of the partition plate (30) in the range of 0.15 to 1.0 mm and preferably from 0.2 to 0.3 mm and that the distance between the partition plate (30) and the surface of the socket (92) is less than 0.35 mm. 3. Device according to claim 1, characterized in that that additional separating parts (32) are provided which are connected to the respective separating plates (30), and that the distance between the additional separating parts (32) and the surface of the bushing (92) is less than 0.35 mm. U. Device according to claim 3, characterized in that the additional separating parts (30) as thin plates are designed that are flexible and rigid. 5. Device according to claim 3 or 1, characterized in that that the additional separating parts (30) are made of plastic film. 6. Device according to one of claims 1 to 5, characterized characterized in that wider parts (27a) at the two ends in the longitudinal direction of the adjustment plate (27) are formed and that the distance between the wider parts (27a) and the surface of the Bushing (92) is less than 0.35 mm. 7. Device according to one of claims 1 to 6, characterized characterized in that wider parts (27a) at the two ends in the longitudinal direction of the adjustment plate (27) are provided and that at least on the wider parts (27a) of the adjusting plate (27) additional Adjusting plates (28) are arranged, the distance between the additional adjusting plate (28) 030036/0 77 2 and the surface area of the socket (92) is less than 0.3-5 mm. 8. Device according to claim 7, characterized in that the additional adjustment plates (28) as thin, flexible and rigid plates are formed. 9. Device according to one of claims 1 to 8, characterized in that the socket (92) extends from magnetized area (M) in axial direction to both ends of the non-magnetized area (N) extends and that the partition plate (30) is arranged on the socket (92) so that it is in Axial direction of the magnetized area (M) to the non-magnetized area (N) at a distance from 1 to 6 mm from the end of the magnetized area (M). 030036/0772